This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The study described in this protocol is an open-label, single arm trial which will evaluate the long-term safety and tolerability of ALTU-135 treatment in patients with CF-related exocrine PI. The study will be conducted at multiple CF centers and each patient will participate for 12 months. Approximately 200 male and female patients with CF-related exocrine PI will be enrolled into the study, including at least 20 children ages 7-11 years. Assuming a withdrawal rate of 20% during the first 6 months and 20% during the second 6 months, 160 patients will complete 6 months of the study and 128 patients will complete the full 1-year.